45 research outputs found
Middle-Field Cusp Singularities in the Magnetization Process of One-Dimensional Quantum Antiferromagnets
We study the zero-temperature magnetization process (M-H curve) of
one-dimensional quantum antiferromagnets using a variant of the density-matrix
renormalization group method. For both the S=1/2 zig-zag spin ladder and the
S=1 bilinear-biquadratic chain, we find clear cusp-type singularities in the
middle-field region of the M-H curve. These singularities are successfully
explained in terms of the double-minimum shape of the energy dispersion of the
low-lying excitations. For the S=1/2 zig-zag spin ladder, we find that the cusp
formation accompanies the Fermi-liquid to non-Fermi-liquid transition.Comment: 4 pages, RevTeX, 3 figures, some mistakes in references are correcte
Antiferromagnetic Zigzag Spin Chain in Magnetic Fields at Finite Temperatures
We study thermodynamic behaviors of the antiferromagnetic zigzag spin chain
in magnetic fields, using the density-matrix renormalization group method for
the quantum transfer matrix. We focus on the thermodynamics of the system near
the critical fields in the ground-state magnetization process(- curve):
the saturation field, the lower critical field associated with excitation gap,
and the field at the middle-field cusp singularity. We calculate magnetization,
susceptibility and specific heat of the zigzag chain in magnetic fields at
finite temperatures, and then discuss how the calculated quantities reflect the
low-lying excitations of the system related with the critical behaviors in the
- curve.Comment: accepted for publication in Physical Review
Reduced Diversity and High Sponge Abundance on a Sedimented Indo-Pacific Reef System: Implications for Future Changes in Environmental Quality
Although coral reef health across the globe is declining as a result of anthropogenic impacts, relatively little is known of how environmental variability influences reef organisms other than corals and fish. Sponges are an important component of coral reef fauna that perform many important functional roles and changes in their abundance and diversity as a result of environmental change has the potential to affect overall reef ecosystem functioning. In this study, we examined patterns of sponge biodiversity and abundance across a range of environments to assess the potential key drivers of differences in benthic community structure. We found that sponge assemblages were significantly different across the study sites, but were dominated by one species Lamellodysidea herbacea (42% of all sponges patches recorded) and that the differential rate of sediment deposition was the most important variable driving differences in abundance patterns. Lamellodysidea herbacea abundance was positively associated with sedimentation rates, while total sponge abundance excluding Lamellodysidea herbacea was negatively associated with rates of sedimentation. Overall variation in sponge assemblage composition was correlated with a number of variables although each variable explained only a small amount of the overall variation. Although sponge abundance remained similar across environments, diversity was negatively affected by sedimentation, with the most sedimented sites being dominated by a single sponge species. Our study shows how some sponge species are able to tolerate high levels of sediment and that any transition of coral reefs to more sedimented states may result in a shift to a low diversity sponge dominated system, which is likely to have subsequent effects on ecosystem functioning. © 2014 Powell et al
A Commentary on “Undergraduate Education: The Implications of Cross-Functional Relationships in Business Marketing–The Skills of High-Performing Managers”
Partial application of insecticide to broad bean (Vicia fabae) as a means of controlling bean aphid (Aphis fabae) and bean weevil (Sitona lineatus)
Microextraction of Nine Haloacetic Acids in Drinking Water at Microgram per Liter Levels with Electrospray-Mass Spectrometry of Stable Association Complexes
Sample preparation based on dynamic ion-exchange solid-phase extraction for GC/MS analysis of acidic herbicides in environmental waters
10.1021/ac991410cAnalytical Chemistry72143077-3084ANCH